Schema:
Staff (staff_id, gender, first_name, last_name, email_address, phone_number)
Customers (customer_id, customer_type_code, address_line_1, address_line_2, town_city, state, email_address, phone_number)
Products (product_id, parent_product_id, product_category_code, date_product_first_available, date_product_discontinued, product_name, product_description, product_price)
Complaints (complaint_id, product_id, customer_id, complaint_outcome_code, complaint_status_code, complaint_type_code, date_complaint_raised, date_complaint_closed, staff_id)
Please answer with SQL.